#define _CRT_SECURE_NO_WARNINGS 1

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head, ListNode* front = nullptr) {
        if (head == nullptr || head->next == nullptr)
        {
            if (head)
                head->next = front;

            return head;
        }
        ListNode* TempNext = head->next;;
        head->next = front;
        return reverseList(TempNext, head);
    }
};